In the entire read process of a flash memory, when the address conversion rate slows down, the flash memory may enter a waiting mode after the current address data is read and before the next address data is read. The low-speed read mode is generally called a data read mode having a lower address conversion rate, and specifically a low-speed read mode of the flash memory is generally defined to be a read mode having a read rate less than 30 MHZ. FIG. 1 is a timing diagram of an existing flash-memory low-speed read mode; the existing flash-memory low-speed read mode includes a normal data read mode, i.e. the mode of the region to which Active in FIG. 1 corresponds and the mode of the region to which Standbye in FIG. 1 corresponds, wherein the time of the data read mode is Ta, and the time of the waiting mode is Ts. The address signal Addres provides address for the read operation; the CEb pin of the flash memory, i.e. the Chip Enable (CE) signal, starts a read process at a low level; the charge pump of the flash memory outputs a voltage VD25_pre in the entire read process; and the clock signal CLK provides a clock signal for the charge pump.
It can be seen from FIG. 1 that the voltage VD25_pre is 3 V in the data read mode when Ta is 30 ns; in the prior art, the output voltage VD25_pre of the charge pump in the data read mode is less than the low threshold voltage of the charge pump, with the low threshold voltage in FIG. 1 being 3.6 V; when the data read is finished, since the output voltage VD25_pre of the charge pump is less than the low threshold voltage, the charge pump will start an automatic charging process, which makes the voltage VD25_pre in the waiting mode increase and up to a high threshold voltage of the charge pump, with the schematic high threshold voltage in FIG. 1 being 5 V; when increasing to the high threshold voltage, i.e. 5 V, the output voltage of the charge pump will start to decrease, and increase again after being as low as the low threshold voltage, i.e. 3.6 V. It can be seen that the charge pump of the flash memory will work and consume the current in the entire waiting mode of the prior art.
The average current in the entire low-speed read mode can be indicated by the following formula:Iavg=(Ta*Ia+Ts*Is)/(Ta+Ts);
wherein Iavg represents the average current in the entire low-speed read mode, Ia represents the current consumed by the flash memory in the data read mode, and Is represents the current consumed by the flash memory in the waiting mode, wherein the current consumed by the flash memory in the waiting mode is mainly the charge-pump current. It can be known that the current consumption in the entire read process is too great due to the presence of Is.